Various documents employ graphic security. The security is implemented to inhibit counterfeiting of the protected documents. There are many forms of graphic security that exist that are both overt and covert, such as watermarks, pantographs, specialty inks, etc. For the most secure documents such as currency, multiple methods are used.
For example, fluorescent microtext and security threads are used on $100 United States currency bills. This is part of an effort to thwart counterfeiters armed with ever more sophisticated computers, scanners and color copiers. The $100 bills, which features the likeness of Benjamin Franklin, is a frequent target of counterfeiters and, accordingly, the currency protection has progressively been enhanced. In 2007, a security thread was added to the $100 bills. The added security thread combines micro-printing with tiny lenses, in the order of 650,000 lenses for a single $100 bill. The lenses magnify the micro-printing such that when the $100 bill is moved from side to side, the image appears to move up and down. And, when the $100 bill is moved up and down, the image appears to move from side to side. Security thread of this type is also used on the Swedish 1,000 kroner note and has been selected for use by the government of Mexico for some higher-denomination notes.
Another example of the use of documents employing graphic security is shown in U.S. Pat. No. 7,422,158 B2 for FLUORESCENT HIDDEN INDICIUM filed Oct. 24, 2003, and assigned to Pitney Bowes Inc. This patent discloses a printed indicia including a first section and a second section. The first section includes a first ink having a first color under normal daylight. The second section includes a second different ink. The second section includes a fluorescent ink which has a second color under normal daylight which is substantially the same as the first color. The fluorescent ink has a fluorescence when subjected to fluorescence-exciting radiation. The second section is embedded with the first section such that the first and second sections are substantially visually indiscernible from each other in normal daylight.
The above security systems are suitable for certain intended purposes; however, for various other applications, it is desirable to have a simple to implement and detect security mark